Process for the formation of phosphoramidates

ABSTRACT

Hydrocarbyl phosphorus acids, preferably hydrocarbyl orthophosphoric acids and hydrocarbyl pyrophosphoric acids are converted to the corresponding phosphoramidates by direct reaction with urea. The phosphoramidates, alone or with a hydrocarbyl phosphorus acid, are useful as additives in petroleum hydrocarbon compositions to which they impart such desirable properties as corrosion resistance.

United States Patent [191 [11] 3,76L$5 Badin [451 Sept. 25, W73

[ PROCESS FOR THE FORMATION OF PHOSPHORAMIDATES Primary Examiner-JosephP. Brust 75 Inventor: Elmer J. Badin, Hightstown, NJ. Rchard Geama [73]Assignee: Cities Service Oil Company, Tulsa,

Okla- 57 ABSTRACT [22] Filed: July 23, 1971 Appl. No.: 165,581

U.S. Cl. 260/984 Field of Search 260/984 Hydrocarbyl phosphorus acids,preferably hydrocarbyl orthophosphoric acids and hydrocarbylpyrophosphoric acids are converted to the corresponding phosphoramidatesby direct reaction with urea. The phosphoramidates, alone or with ahydrocarbyl phosphorus acid, are useful as additives in petroleumhydrocarbon compositions to which they impart such desirable prop ertiesas corrosion resistance.

8 Claims, N0 Drawings PROCESS FOR THE FORMATION OF PHOSPHORAMIDATESBACKGROUND OF THE INVENTION thophosphoryl chloride. A typical example ofthe prior art process is the reaction of ammonia with diethylorthophosphoryl chloride:

One readily apparent deficiency of the above prior art process is thatlow overall yields of the orthophosphoramidate are obtianed because theusual procedure requires preparation of diethyl orthophosphoryl chloridein low yield by reaction of ethanol with phosphoryl chloride. Inaddition, the orthophosphoramidate product must be separated from theby-products of acidic ammonium chloride and traces of corrosive hydrogenchloride. There is thusan added expense inherent in the use of the priorart process.

SUMMARY It is an object of this invention to provide a novel process forthe conversion of hydrocarbyl phosphorus acids to the correspondingphosphoramidates.

It is another object of this invention to provide an economical processfor the conversion of hydrocarbyl phosphorus acids to the correspondingphosphoramidates which does not involve the formation of corrosiveby-products.

It is a particular object of this invention to provide a novel processfor the conversion of hydrocarbyl orthophosphoric acids and hydrocarbylpyrophosphoric acids to the corresponding hydrocarbyl phosphoramidates.

Other objects will be apparent to those skilled in the art from thedisclosure contained herein.

The foregoing objects are attained according to the process of thisinvention. Broadly, this invention consists of a process for theconversion of hydrocarbyl phosphorus acids to the correspondinghydrocarbyl phosphormidates comprising reacting urea with a hydrocarbylphosphorus acid selected from the group consisting of hydrocarbylorthophosphoric acids and hydrocarbyl pyrophosphoric acids.

By proceeding according to the process of this invention, it is possibleto readily and economically convert a hydrocarbyl phosphorus acid to thecorresponding hydrocarbyl phosphoramidate. The process is characterizedby the absence of by-product hydrogen halide or ammonium halide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention is concernedwith a novel process for the conversion of hydrocarbyl phosphorus acidsto the corresponding hydrocarbyl phosphoramidates. Broadly, the processinvolves the reaction of the hydrocarbyl phosphorus acid with urea toform the hydrocarbyl phosphoramidate. The process is characterized bythe absence of corrosive by-products. The process requires that thehydrocarbyl phosphorus acid have at least one OH group bonded tophosphorus. The reaction occurring in the process of the instantinvention is typified by the reaction of diethyl orthophosphoric acidwith urea.

The process of this invention is especially useful in the conversion ofhydrocarbyl orthophosphoric acids and hydrocarbyl pyrophosphoric acidsto the corre' sponding hydrocarbyl phosphoramidates. It is essentialthat the hydrocarbyl phosphorus acid have at least one OI-Igroup bondedto phosphorus. Thus, in the case of hydrocarbyl orthophosphoric acids,either monohydrocarbyl orthophosphoric acid or dihydrocarbylorthophosphoric acid may be converted to the corresponding hydrocarbylphosphoramidates. By the same token, hydrocarbyl pyrophosphoric acidsuseful in the practiceof this invention may be monohydrocarbyl,dihydrocarbyl, or trihydrocarbyl pyrophosphoric acids. In the case wherethe hydrocarbyl phosphorus acid contains more than one OH group bondedto phosphorus, all or part of the OH groups may be replaced by NHgroups. However, it appears mostlikely that only one OH group bonded toany one phosphorus is easily replaced by Nl-I since the first OH groupappears to be more reactive than the second. Thus, for example, amonohydrocarbyl pyrophosphoric acid is preferably converted to themonohydrocarbyl pyrophosphordiamidate.

In the above equation, R represents a hydrocarbyl group.

The hydrocarbyl groups of the hydrocarbyl phosphorus acids may bealiphatic, aromatic, naphthenic, or may contain various mixtures ofaliphatic, aromatic, and naphthenic portions. Aliphatic and naphthenicgroups may be either saturated or unsaturated. In addition, thehydrocarbyl groups in any one hydrocarbyl phosphorus acid containingmore than one hydrocarbyl group may be either the same or different.While the choice of hydrocarbyl groups in the hdyrocarbyl phosphorusacids is not critical, alkyl groups are preferred. Most preferred arebranched chain alkyl groups. The size of the hydrocarbyl groups is notcritical. However, the hydrocarbyl groups generally contain about i to55 carbons, and preferably about 5 to 35 carbons. Especially preferredare hydrocarbyl groups containing about 8 to 20 carbons. Following areexamples of hydrocarbyl phosphorus acids that may be converted tohydrocarbyl phosphoramidates by the process of this invention.

Dimethyl orthophosphoric acid Mono-p-tolyl orthophosphoric acidDi(2-ethylhexyl) orthophosphoric acid Cyclohexyl eicosyl orthophosphoricacid Monoisooctyl orthophosphoric acid Diisooctyl orthophosphoric acidDiphenyl orthophosphoric acid Monooctadecyl orthophosphoric acid Heptyltriacontyl orthophosphoric acid Tripropyl pyrophosphoric acidZ-Ethylhexyl isooctyl pyrophosphoric acid Phenyl pyrophosphoric acidp-Tolyl nonyl pyrophosphoric acid Tricyclohexyl pyrophosphoric acidUndecyl eicosyl pyrophosphoric acid Dimethyl pyrophosphoric acid Ifdesired, various mixtures of the above hydrocarbyl phosphorus acids maybe used. It will be understood that the foregoing hydrocarbyl phosphorusacids are merely illustrative and applicant does not restrict hisinvention thereto. However the preferred hydrocarbyl phosphorus acidsare hydrocarbyl orthophosphoric acids, particularly di(2-ethylhexyl)orthophosphoric acid and mixtures of monoisooctyl orthophosphoric acidand diisooctyl orthophosphoric acid.

The amount of urea to be reacted with the hydrocarbyl phosphorus acidwill generally be about 1 mole of urea for each equivalent of OH groupsof the hydrocarbyl phosphorus acid that is to be converted to NH groups.Thus, 1 mole of a dihydrocarbyl orthophosphoric acid will be reactedwith about 1 mole of urea. Similarly, 1 mole of a monohydrocarbylorthophosphoric acid can be reacted with about 2 moles of urea if thedesired product is the monohydrocarbyl orthophosphordiamidate or withabout 1 mole of urea if the desired product is the monohydrocarbyl acidorthophosphoramidate. It is apparent that from the stoichiometry of theprocess as disclosed herein, one skilled in the art will be able todetermine the ratio of urea to hydrocarbyl phosphorus acid to obtain thedesired product.

The process of the instant invention is usually carried out in an inertsolvent in which the reactants are soluble or may be rendered soluble asby heating, but choice of solvents is not critical and is well withinthe capability of one skilled in the art to make. However, it has beenfound that toluene is generally a preferred solvent.

The choice of the reaction temperature employed in the process of thisinvention is empirical. Generally, a temperature sufficiently high tocause solution of the reactants is the minimum employed. Reactiontemperatures within the range of about 100200C., and preferably about110155C., are usually employed.

The course of the reaction is readily followed by the evolution ofammonia. The reaction is generally complete when evolution of ammoniaceases. Thus, the reaction time will vary depending on such factors asthe reactivity of the OH group in the phosphorus acid and the reactiontemperature, i.e., the higher the temperature, the shorter the reactiontime as a rule. Thus, the reaction time will vary depending on thereactivity of the OH group and on reaction conditions. The optimumreaction time will be within the ability of one skilled in the art todetermine, based on these factors.

This invention will be further illustrated by the following specificexamples.

EXAMPLE I In a round bottom flask fitted with a stirrer and refluxcondenser are placed 200 ml. of reagent grade toluene, 161.0 g. (0.500mole) of di(2'ethylhexyl) orthophosphoric acid, and 30.0 g. (0.500 mole)of reagent grade urea. The stirred reaction mixture is then heated underreflux. The urea, which is initially insoluble in the cold toluene, goesinto solution as the reflux temperature is approached. After aboutone-half hour of stirring the reaction mixture under reflux, evolutionof ammonia is detected. The mixture is stirred under reflux for a totalof 9 hours at which point the evolution of ammonia has ceased. Thereaction mixture, which contains a white precipitate believed to bedecomposition products of urea such as biuret and cyanuric acid, isfiltered. The filtrate is distilled under a reduced pressure of 17 mm.of Hg to leave a clear, tan, oily liquid residue weighing 161.7 g. asthe reaction product. lnfrared spectroscopy of the product as evidencedby absorption bands in the region 3,5003,000 emf, indicates N-Hstretching of the P-NH group. in addition, elemental analysis of 2.74percent nitrogen by the Kjeldahl method indicates the reaction productto be a mixture of about 2 parts di(2-ethylhexyl) orthophosphoramidateand about 1 part unreacted di(2-ethylhexyl) orthophosphoric acid.

EXAMPLE ll Example 1 is substantially repeated using 200 ml. of reagentgrade toluene, a quantity of an approximately equimolar mixture ofmonoand diisooctyl orthophosphoric acids sufficient to contain 1.08equivalents of OH groups, and 1 mole of reagent grade urea. The stirredreaction mixture is heated under reflux. The initially insoluble ureadissolves when the pot temperature reaches about 113 C. The reactionmixture is stirred under reflux for a total of about 17.6 hours duringwhich time the pot temperature varies from about 1 15 C. to a peak ofabout 190 C. Apart from a period of about 1 hour when the pottemperature reaches a peak of about 190 C., the pot temperature ismaintained within the range of about 115153 C. Evolution of ammonia isfirst detected after about one-half hour of refluxing. Ammonia is stillbeing evolved at the end of the approximately 17.6 hour reflux periodwhen the reaction is stopped.

The reaction mixture is then filtered to remove a white precipitatebelieved to be decomposition products of urea such as biuret andcyanuric acid. The filtrate is distilled under reduced pressure leavinga clear, viscous liquid weighing 160.8 g. as the reaction product.Elemental analysis shows the reaction product to contain 2.37 percentnitrogen as determined by the Kjeldahl method. An infrared spectrum ofthe product has bands in the region 3,5003,000 cm."

While the instant invention has been illustrated by certain specificexamples, it will be appreciated by those skilled in the art that theprocess of the invention is broadly operable on hydrocarbylorthophosphoric acids and hydrocarbyl pyrophosphoric acids. The primaryrequirement is that the hydrocarbyl phosphorus acid contain at least oneOH group bonded to phosphorus.

Hydrocarbyl orthophosphoramidates are known I as additives for use inpetroleum hydrocarbon products. For example, they are used in leadedgasoline compositions for the purpose of reducing surface ignition andspark plug fouling. l have found that mixtures of hydrocarbylorthophosphoramidates and the unreacted hydrocarbyl orthophosphoric acidprecursor, when incor porated in petroleum hydrocarbon products, impartthereto excellent anti-corrosion properties. Mixtures of hydrocarbylorthophosphoramidates and unreacted hydrocarbyl orthophosphoric acids inthe desired proportions may be obtained by the process of thisinvention. The degree of conversion of the hydrocarbyl orthophosphoricacid to the hydrocarbyl orthophosphoramidate is readily controlled byvarying the amount of urea and proper choice of reaction parameters suchas temperature and reaction time.

It will be understood that the specific embodiments set forth herein areillustrative only and the invention is not to be limited except as setforth in the following claims.

I claim:

1. A process for the conversion of a hydrocarbyl phosphorus acid to thecorresponding hydrocarbyl phosphoramidate by conversion of OH groupsbonded to the phosphorus of said acid to NH groups comprising reactingat a temperature within the range of about l00200 C 1 mole of urea perequivalent of said OH groups to be converted to Nl-l wherein saidhydrocarbyl phosphorus acid is selected from the group consisting ofhydrocarbyl orthophosphoric acid and hydrocarbyl pyrophosphoric acid andwherein each hydrocarbyl group of said acid contains about 1 to 55carbons.

2. The process of claim 1 wherein the hydrocarbyl phosphorus acid is ahydrocarbyl orthophosphoric acid in which the hydrocarbyl groups arealkyl groups.

3. The process of claim 2 wherein the alkyl groups are branched.

4. The process of claim 3 wherein the branched alkyl groups containabout 5 to'35 carbons.

5. The process of claim 4 wherein the reaction is carried out at atemperature in the range of about 1 10l 55 C.

6. The process of claim 5 wherein the reaction is carried out in tolueneas the solvent.

7. The process of claim 6 wherein the hydrocarbyl orthophosphoric acidis di(2-ethylhexyl) orthophosphoric acid.

8. The process of claim 6 wherein the hydrocarbyl orthophosphoric acidis a mixture of monoisooctyl orthophosphoric acid and diisooctylorthophosphoric acid.

2. The process of claim 1 wherein the hydrocarbyl phosphorus acid is ahydrocarbyl orthophosphoric acid in which the hydrocarbyl groups arealkyl groups.
 3. The process of claim 2 wherein the alkyl groups arebranched.
 4. The process of claim 3 wherein the branched alkyl groupscontain about 5 to 35 carbons.
 5. The process of claim 4 wherein thereaction is carried out at a temperature in the range of about 110*-155*C.
 6. The process of claim 5 wherein the reaction is carried out intoluene as the solvent.
 7. The process of claim 6 wherein thehydrocarbyl orthophosphoric acid is di(2-ethylhexyl) orthophosphoricacid.
 8. The process of claim 6 wherein the hydrocarbyl orthophosphoricacid is a mixture of monoisooctyl orthophosphoric acid and diisooctylorthophosphoric acid.